GRB 100413A

S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB),
M. M. Chester (PSU), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), E. A. Hoversten (PSU),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
N. P. M. Kuin (UCL-MSSL), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), A. Rowlinson (U Leicester),
B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU),
M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU),
G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 17:33:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100413A (trigger=419404).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 266.217, +15.837 which is 
   RA(J2000)  =  17h 44m 52s
   Dec(J2000) = +15d 50' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 15 sec.  The peak count rate
was ~700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 17:35:48.4 UT, 140.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source located at RA, Dec 266.22043, 15.83309 which
is equivalent to:
   RA(J2000)  = 17h 44m 52.90s
   Dec(J2000) = +15d 49' 59.1"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 18 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (7.3e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2 (+1.81/-1.60)
x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 6.30e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 149 seconds after the BAT trigger. No credible
afterglow candidate has  been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of  the XRT error circle. The typical
3-sigma upper limit has been about 19.6 mag.  The 8'x8' region for the
list of sources generated on-board covers 100% of the  XRT error
circle. The list of sources is typically complete to about 18 mag. No 
correction has been made for the expected extinction corresponding to
E(B-V) of  0.11. 

Burst Advocate for this burst is S. T. Holland (Stephen.T.Holland AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok, O.Gres, O.
Irkutsk State University


K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok, O.Gres, 
O. Chuvalaev
Irkutsk State University

V.Yurkov, 
Yu.Sergienko, D.Varda, A.Garusina Blagoveschensk Educational State 
University, Blagoveschensk


E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, 
D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zemnukhov, 
M. Kornilov
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory


V.Krushinski, I.Zalozhnih, T.Kopytova, A.Popov
Ural State University, Kourovka




Two MASTER  robotic telescopes (MASTER-Net: http://observ.pereplet.ru, 
testing telescopes)
located at Baykal-Tunka and Blagoveschensk   was responted to the  GRB 
100413A (Swift Bat alert,
  Holland et al, GCN CIRC 10581
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 )   32 sec after   Notice time and  65 s 
after the GRB time.

There is now OT on the first 20-s  exposition time unfiltered images 
inside Swift XRT error box (Holland et al., GCN CIRC 10581
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 )
brighter 17.0 (Blagoveschensk) and 16.6 (Baykal-Tunka).




The message may be cited.

mailto: lipunov@sai.msu.ru

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 952 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 100413A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 266.22175, +15.83400 which is equivalent
to:

RA (J2000): 17h 44m 53.22s
Dec (J2000): +15d 50' 02.4"

with an uncertainty of 1.8 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 100413A (trigger #419404)
(Holland, et al., GCN Circ. 10581
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 ).  The BAT ground-calculated position is
RA, Dec = 266.223, 15.833 deg, which is 
   RA(J2000)  =  17h 44m 53.4s 
   Dec(J2000) = +15d 50' 00.3" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
 
The mask-weighted light curve shows multiple overlapping peaks in two main
clusters of peaks.  It starts at ~T-45 sec, with the first cluster ending 
at ~T+40 sec.  The second cluster starts around T+90 sec, peaks around T+100 sec,
and ends later than T+240 sec.  The emission does not return
to background between the two clusters.  We are issuing this refined circular
prior to receiving all the data, because there is a backlog in the downlinking
of the data and it will be many hours until receive the data past T+240 sec.
These results will be updated when we receive the full data set.
 
Using this partial data set, the time-averaged spectrum
from T-1.5 to T+213.1 sec is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 1.17 +- 0.07.
The fluence in the 15-150 keV band is 6.2 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+116.78 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/419404/BA/

P.A. Evans (U. Leicester) and S. T. Holland (CRESST/USRA/GSFC) report on
behalf of the Swift-XRT team:

We have analysed 5.3 ks of XRT data for GRB 100413A (Holland et al. GCN
Circ. 10581
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 ), from 129 s to 30.4 ks after the BAT trigger. The data
comprise 551 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Goad et al.
(GCN. Circ 10584).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.53 (+/- 0.07). At T+430 s the decay
flattens to an alpha of 1.20 (+/- 0.04). The light curve breaks again
at T+9980 s to a poorly-constrained final decay with alpha=2.3 (-0.5,
positive error is unconstrained).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.83 (+/-0.06). The
best-fitting absorption column is 2.42 (+0.19, -0.18) x 10^21 cm^-2, in
excess of the Galactic value of 7.3 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.06 (+0.13, -0.12)
and a best-fitting absorption column of 3.1 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.5 x 10^-11 (7.4 x 10^-11) erg cm^-2
count^-1.

If the light curve continues to decay with a power-law decay index of
2.3, the count rate at T+24 hours will be 2.02 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x
10^-14 (1.5 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00419404.

This circular is an official product of the Swift-XRT team.

Adria C. Updike, Dieter H. Hartmann (Clemson University), Loris Magnani
(UGA), and Chris De Pree (Agnes Scott College) report:

We observed the field of GRB 100413A (Holland et al., GCN 10581
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 ) with the
0.9m SARA-North telescope at KPNO beginning at 06:57 UT on April 14, 2010
(13.4 hours after the trigger) at high airmass and continuing for 40
minutes.  At the location of the enhanced XRT error circle (Goad et al.,
GCN 10584
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 ) we do not detect any new sources in stacked I-band images down
to a limiting magnitude of I ~ 19 (as compared to the USNO B1.0 catalog). 
No further observations are planned.

S. Campana (INAF-OAB), P.A. Evans (U. Leicester) and S. T. Holland
(CRESST/USRA/GSFC) report on behalf of the Swift-XRT team:

Swift XRT observed GRB 100413A (Holland et al. 2010, GCN 10581
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 )
in Windowed Timing (WT) mode in the 146-550 s time interval.
During this interval the 1.5-10 keV to 0.3-1.5 keV hardness ratio slightly
decayed, testifying for small spectral variations.
We assume a Galactic column density of 7.3x10^20 cm^-2 (Kalberla et
al. 2005, A&A 440 775) and fit the WT spectrum with an absorbed
(tbabs*ztbabs) cutoff power law model within XSPEC (the cutoff power
law model provides much better results in terms of column density 
evaluation
with respect to a simple power law model when small spectral variations 
are present).
Data were grouped to have 30 counts per spectral bin. The resulting fit 
is good
(reduced chi2=0.9, 194 dof).
Filtering the data for single pixel events does not change the results.
In the intrinsic column density vs. redshift plane there is a low 
significance (3 sigma)
solution at low redshifts but the minimum lies at higher redshifts with 
a 2 sigma confidence
level solution of z=3.9+1.7-0.7 and N_H(z)=(5.5+9.8-2.1)x1022 cm-2.
Thus, even if we cannot exclude that GRB100413A is at low redshift, a 
high redshift (z~4),
highly absorbed (N_H(z)~6x1022 cm-2) solution is preferred.
This compares well with the non-detection with UVOT (Holland et al. 
2010) and
other robotic telescopes.

The contour plot is available at
http://www.brera.inaf.it/utenti/campana/100413.gif

C. Guidorzi (U. Ferrara), R.J. Smith (Liverpool JMU),
N. Tanvir (U. Leicester), I.A. Steele, S. Kobayashi,
C.G. Mundell, D. Bersier, Z. Cano, N.R. Clay, A. Melandri,
C.J. Mottram (Liverpool JMU), A. Gomboc (U. Ljubljana)
report on behalf of a large collaboration:

On 2010 April 13 at 17:37:19 UT the 2-m Faulkes Telescope South
automatically began observing the Swift GRB 100413A
(Holland et al., GCN Circ. 10581
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 ) using the BVR, i' filters,
corresponding to 231 s after the burst trigger time.

Inside the XRT error circle (Goad et al. GCN Circ. 10584
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 )
we do not detect any source at the following limiting
magnitudes:

Mid time from    Total Exp   Filter    Magnitude
trigger (min)    (s)
------------------------------------------------
04.52            3x10        R         > 19.8
28.6              540        R         > 22.2
33.2              520        i         > 21.3
------------------------------------------------

Magnitudes have been calibrated from nearby USNOB-1
stars, using the R2 and I magnitudes.

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P.
Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind
team report:

The long GRB 100413A (Swift-BAT trigger #419404: Holland et al., GCN 
10581
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 ; Stamatikos et al., GCN 10585
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 ) was detected by Konus-Wind in the 
waiting mode.

The burst light curve shows a multipeaked structure with a total 
duration of ~220 s.

As observed by Konus-Wind, the burst had a fluence of (2.66 +/-
0.23)x10^-5 erg/cm2 (in the 20 - 1200 keV energy range).

Modeling the K-W 3-channel time-integrated spectrum (from T0-3 s to 
T0+212 s) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.01 � 0.06, Ep = 446 +/- 123 keV.

All the quoted errors are estimated at the 1 sigma confidence level.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB100413A/

Assuming z ~ 3.9 (Campana, Evans, and Holland, GCN 10588
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 ) and a standard 
cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 
0.73, the isotropic energy  release is E_iso ~8x10^53 erg, and Ep_rest 
~2200 keV.

F.E. Marshall (NASA/GSFC) and S.T. Holland (CRESST/USRA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 100413A
150 s after the BAT trigger (Holland et al., GCN Circ. 10581
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 ).
No optical afterglow consistent with the enhanced XRT position
(Goad et al., GCN Circ. 10584
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 ) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposures and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           150          300          147         >20.5
u_FC               308          558          246         >20.5
white              150         6231          589         >21.8
v                  639         6641          490         >20.4
b                  564         7321          353         >20.7
u                  308         7256          717         >20.7
w1                 688         7051          471         >20.5
m2                 663         6846          490         >20.4
w2                 614         6436          491         >20.8

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.11 in the direction of the burst
(Schlegel et al. 1998).

Robert Filgas, Thomas Kruehler, Jochen Greiner and Abdullah Yoldas (all 
MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 100413A (Swift trigger 419404; Holland et 
al., GCN #10581
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et 
al., 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La 
Silla Observatory (Chile).

Observations started at 05:43 UT on April 14, 12 hours after the GRB 
trigger, and continued for 2.5 hours. They were performed at an average 
seeing of 1" under clear sky conditions.

In stacked images of 125 min total integration time in g'r'i'z' and 100 
min in JHK, we do not detect a source within the Swift/XRT error circle 
(Goad et al., GCN #10584
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 ) down to the following 3 sigma limiting 
magnitudes (all in the AB system):

g' > 25.3,
r' > 25.2,
i' > 24.6,
z' > 24.3,
J > 22.5,
H > 22.1 and
K > 21.1

These limits were derived by calibrating the images against the GROND 
zeropoints and 2MASS field stars and are not corrected for the Galactic 
foreground extinction corresponding to a reddening of E_(B-V)= 0.11 in 
the direction of the burst (Schlegel et al. 1998).

S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), S. T. Holland (CRESST/USRA/GSFC)
(for the Swift-BAT team):
 
The full data set for this burst has been downlinked.
Using the data set from T-239 to T+963 sec, we report final analysis
of BAT GRB 100413A (trigger #419404) (Holland, et al, GCN Circ 10581
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and Stamatikos, GCN Circ 10585
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 ).  The BAT ground-calculated position is
RA, Dec = 266.223, 15.835 deg, which is 
   RA(J2000)  =  17h 44m 53.6s 
   Dec(J2000) = +15d 50' 04.6" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
 
The mask-weighted light curve shows multiple overlapping peaks in two main
clusters of peaks.  It starts at ~T-45 sec, with the first cluster ending
at ~T+40 sec.  The second cluster starts around T+90 sec, peaks around T+100 sec,
and ends at ~T+250 sec.  The emission does not return to background
between the two clusters.  T90 (15-350 keV) is 191 +- 14 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-3.4 to T+227.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.25 +- 0.07.  The fluence in the 15-150 keV band is 6.2 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+116.78 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/419404/BA/

S. Sugita (Nagoya U.), K. Yamaoka (Aoyama  Gakuin U.), M. Ohno,
M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, M. Suzuki,
T. Tamagawa (RIKEN), N. Vasquez (Tokyo Tech.), Y. Urata, H.M. Lin,
P. Tsai (NCU), Y. Nishioka, N. Ohmori, A. Daikyuji, E. Sonoda, K. Kono,
K. Noda, M. Yamauchi (Univ. of Miyazaki), T. Sugasahara, M. Tashiro,
Y. Terada, W. Iwakiri (Saitama U.), Y. Hanabata, T. Uehara,
T. Takahashi, Y. Fukazawa (Hiroshima U.), T. Enoto, K. Nakazawa,
K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.),
on behalf of the Suzaku WAM team, report

The very long GRB 100413A (Swift/BAT trigger #419404 ;
Holland et al., GCN 10581
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 )

was detected by the the Suzaku Wide-band  All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at 2010-04-13 17:33:28 UT
(=T0).

The observed light curve shows a multi-peaked structure
 lasting to T0+220s with a duration T90 of about 160 seconds.
The fluence in 100 - 1000 keV was 1.59 (-0.83, +0.21) x10^-5 erg/cm^2.
 The 1-s peak flux measured from T0+118s was 0.38 (-0.27, +0.14)
photons/cm^2/s in the same  energy range.

Preliminary result shows that the time-averaged spectrum from
T0-2s to T0+213s is well fitted by a power-law with exponential
cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       -0.59 (-1.64, +1.27), and
  Epeak       364 (-55, +98) keV (chi^2/d.o.f. = 37.9/30).

All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves with 1-sec time resolution for this burst will be appeared
at:


http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html

Dale A. Frail (NRAO) and Derek Fox (PSU) report on behalf of a larger
collaboration:

"We used the Expanded Very Large Array (EVLA) to observe the
localization of the Swift burst GRB 100413A (Trigger #419404; Holland
et al., GCN 10581
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 ), an X-ray bright event without any optical or NIR
counterpart to deep limits (Xin et al., GCN 10583
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 ; Updike et al., GCN
10587
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 ; Guidorzi et al., GCN 10589
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 ; Filgas et al., GCN 10592
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 ). Within
the revised XRT error circle (Goad et al., GCN 10584
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 ) we detect a
single 8.5 GHz radio source with flux density 159 +/- 15 uJy and
position R.A. 17:44:53.16, Dec. +15:50:03.2 (J2000), with 1-sigma
astrometric uncertainty of +/-0.6 arcsec.

The EVLA is undergoing active commissioning and as such these results
should be considered preliminary. Further observations are planned.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."

Sayan Chakraborti, Naveen Yadav and Alak Ray (Tata Institute of
Fundamental Research, Mumbai, India) report:

We observed the optically dark GRB 100413A, whose radio afterglow has
been detected by the EVLA at 8.5 GHz (Frail et al, GCN 10611
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 ), with
the Giant Metrewave Radio Telescope (GMRT) on April 19.1 UT. We do
not find, any source at its position, at the observing frequency of
1.28 GHz, down to the 3 sigma upper limit of 124 uJy.

We thank the staff of the GMRT that made this observation possible.
GMRT is run by the National Centre for Radio Astrophysics of the Tata
Institute of Fundamental Research.